Babometeb



UNITED STATES PATENT OFFICE.

L. WOODRUFF, OF ANN ARBOR, MICHIGAN.

BAROIVIETER.

Specification of Letters Patent No. 28,626, dated June 5, 1860.

To all 'whom it may concern:

Be it known that I, LUM WOODRUFF, of Ann Arbor, in the county ofWashtenaw and State of Michigan, have invented certain new and usefulImprovements in Mercurial Barometers; and I do hereby declare that thefollowing is a full, clear, and eX- act description of the same,reference being had to the accompanying drawings, forming part of thisspecification, in which- Figure l is a central vertical section o f abarometer with my improvements. Fig. 2 isa vertical section of thecisterns on a larger Scale than Fig. l. Fig. 3 is a horizontal sectionof the same.

Similar letters of reference indicate corresponding parts in the severalfigures.

To enable others skilled in the art to make and use my invention I willproceed to describe its construction and operation.

A, is the cistern, and B, the reservoir made of cast iron in one piece,the cistern having an opening at the top, and a closed bottom and thereservoir being made open throughout, and closed at topfand bottom byStoppers a, a, made air tight with cement. C, is the tube cemented intothe cistern, and dipping to within a short distance of the bottomthereof.

D, is the valve for closing the lower end of the tube, attached looselyto the upper end of an upright screw E, which screws through a tappedopening in the bottom of the cistern. This valve is faced with a pieceof stout india-rubber or other fieXible and elastic substance Z), toprevent its injuring the tube, and to enable it to make a tight jointwith the bottom thereof, and at the back of this rubber a cavity c, isformed in the valve to allow the rubber to yield to any expansion of themercury that may take place when the tube is filled and the valveclosed, and thereby to prevent the bursting of the tube. I will hereremark, however, that before letting the mercury fill the tube andshutting it in, the instrument should be placed where the temperature isfrom 80 to 90o F., and in that case there will be little danger ofsubsequent expansion.

F, is the screw plug for closing the orifice of communication (Z,between the cistern and t-he reservoir, said plug screwing through atapped hole e, in the back of the reservoir opposite to the orifice ci,which is tapped with a taper tap so that 'the plug may screw into itvery tightly. VWhen the plug is screwed up into the lorifice d, it alsofits closely into the hole e, but when it is unscrewed from (Z, a flatplace or recess f, which is filed or out in one side of it is broughtinto the Ahole e, forming a passage for the admission of air to thereservoir from which it passes through the orifice d, into the cisternA. The lower edge of the orifice cl, is at the required level of themercury in the cistern, and all the surplus mercury runs through thesaid orifice into the reservoir. The cistern A, and the whole of thetube C, except the indicating` portion, are inclosed within a tubularcasing Gr, of wood or other material, the inclosed portion of the tubebeing wound around with paper, cloth, or other soft material g, (Fig. l)to form a packing filling the space between it and the casing, andthereby being protected from breakage.

To bring this barometer from the operative condition, shown in Fig. l,to the portable' condition, illustrated in Fig. 2, 'it is first placedhorizontally with the reservoir B, upward and then shaken or jarred tomake enough of the mercury from the cistern A, run into the tube C, tofill it, and the spare mercury from the reservoir B, run into thecistern to fill that completely. The screw plug F, is then screwed intightly and the screw E, afterward screwed in to close the bottom of thetube C, by the valve D, and this being done it may be carried -in anyposit-ion, and will bear any amount of jarring or throwing about that itis likely to receive in transportation, Without injury.

To bring it from the portable to the op-I erative condition, it is firstplaced lupside down, and while in this position the screw E, isunscrewed to open the valve D, and the barometer is jarred and shakenfor a time to expel from the tube into the cistern any small quantity ofair that may have accidentally entered the tube in packing fortransportation. It is then hung up, and the plug F, unscrewed to let thesurplus mercury out of the cistern into the reservoir.

I do not claim the reservoir for containing mercury t0 fill up theeistern; ner yet to tbe reservoir and eistern, substantially as, the useof a valve or cock to close the comherein described, and operating asherein set munication between the reservoir and cisforth.

tern. But LUM WOODRUFF. 5 What I claim as my invention, and de-Witnesses:

sire to secure by Letters Patent, is GEORGE C. MAYNARD,

The screw plug constructed and applied FRASER.

